The present invention relates to a dynamic microphone, more particularly to a dynamic microphone with a moving coil type microphone unit.
FIG. 1 is a conventional cross-sectional view of a dynamic microphone which has been disclosed as a means of attaining a full understanding of the present invention. In FIG. 1, a moving coil type microphone unit 2 for collecting sound is mounted on a packing 3 in a microphone casing 1 and a moving coil type vibration pickup unit 4 is also positioned therein. The moving coil type vibrating pickup unit 4 is mounted through a rubber spacer 6 to a supporting member 5 fixed to the case 1. The microphone unit 2 and the vibration pickup unit 4 are electrically connected in opposite phase in order to cancel noise components arising from vibrations transmitted to the case 1. The output signal from the microphone unit and the vibration pickup unit is coupled to output terminals 7a and 7b.
With such a construction, since the microphone unit 2 is disposed far from the pickup unit 4, as is apparent from FIG. 1, vibrations transmitted to the microphone case 1 will only be cancelled positively at low frequencies. Namely, for high frequencies, since there is a phase difference between outputs of the microphone unit 2 and vibration pickup unit 4, is it impossible to obtain sufficient cancellation of the noise components. Also, the prior art device of FIG. 1 requires separate magnetic circuits for the microphone unit 2 and for the vibration pickup unit 4, resulting in an increase in the number of mechanical parts and hence a high cost.